to to the genus . Strain EG1HP4QL produced an extracellular polysaccharide (EPS), with production - 1 peaking (5.9 g L ) during growth on medium S-G containing 2% (w/v) sucrose at 35 °C (pH 8.0). The EPS had significant emulsifying activity (E %) against kerosene (65.7 ± 0.8%), o - xylene (64.0 ± 1%), and sunflower oil 24 (44.7 ± 0.5%). The composition of the EPS included two polymers- a negatively charged and a neutral one (~ 3:1) - in which mannose and glucose were the main neutral monosaccharide constituents. Strain EG1HP4QL was able to utilize crude oil (35.3%) as the sole carbon source within 12 days. The minimum inhibitory concentrations of heavy metals [Zn(II), Cd(II), Pb(II), Ni(II), and Cu(II)] for strain EG1HP4QL were 1.0, 2.0, 2.0, 2.5, and 5 mM, respectively.

Igarashi, K., Miyako, E., Kato, S., 2020. Direct interspecies electron transfer mediated by graphene oxide-based materials. Frontiers in Microbiology 10, 3068. doi: 10.3389/fmicb.2019. 03068. https://www.frontiersin.org/article/10.3389/fmicb.2019. 03068

Conductive materials are known to promote direct interspecies electron transfer (DIET) by electrically bridging microbial cells. Previous studies have suggested that supplementation of graphene oxide (GO) based materials, including GO, and reduced GO (rGO), to anaerobic microbial communities, can promote DIET. This promotion mechanism is thought to be involved in electron transfer via rGO or biologically formed rGO. However, concrete evidence that rGO directly promotes DIET is still lacking. Furthermore, the effects of the physicochemical properties of GO-based materials on DIET efficiency have not been elucidated. In the current work, we investigated whether chemically and biologically reduced GO compounds can promote DIET in a defined model coculture system, and also examined the effects of surface properties on DIET-promoting efficiency. Supplementation of GO to a defined DIET coculture composed of an ethanol-oxidizing electron Geobacter metallireducens Methanosarcina barkeri producer and a methane-producing electron consumer promoted methane production from ethanol. X-ray photoelectron spectroscopy revealed that GO was reduced to G. metallireducens rGO during cultivation by activity. The stoichiometry of methane production from ethanol and the isotope labeling experiments clearly showed that biologically reduced GO induced DIET-mediated syntrophic methanogenesis. We also assessed the DIET-promoting efficiency of chemically reduced GO and its derivatives, including hydrophilic amine-functionalized rGO (rGO-NH ) and hydrophobic octadecylamine- 2 functionalized rGO (rGO-ODA). While all tested rGO derivatives induced DIET, the rGO derivatives with higher hydrophilicity showed higher DIET-promoting efficiency. Optical microscope observation revealed that G. metallireducens microbial cells, in particular, , more quickly adhered to more hydrophilic GO-based materials. The superior ability to recruit microbial cells is a critical feature of the higher DIET-promoting efficiency of the hydrophilic materials. This study demonstrates that biologically and chemically reduced GO can promote DIET-mediated syntrophic methanogenesis. Our results also suggested that the surface hydrophilicity (i.e., affinity toward microbial cells) is one of the important determinants of the DIET-promoting efficiencies. These observations will provide useful guidance for the selection of conductive particles for the improvement of methanogenesis in anaerobic digesters.

Imachi, H., Nobu, M.K., Nakahara, N., Morono, Y., Ogawara, M., Takaki, Y., Takano, Y., Uematsu, K., Ikuta, T., Ito, M., Matsui, Y., Miyazaki, M., Murata, K., Saito, Y., Sakai, S., Song, C., Tasumi, E., Yamanaka, Y., Yamaguchi, T., Kamagata, Y., Tamaki, H., Takai, K., 2020. Isolation of an archaeon at the prokaryote - eukaryote interface. Nature 577, 519-525.

https://doi.org/10.1038/s41586-019-1916-6 The origin of eukaryotes remains unclear. Current data suggest that eukaryotes may have emerged from an archaeal lineage known as 'Asgard' archaea. Despite the eukaryote -like genomic features that are found in these archaea, the evolutionary transition from archaea to eukaryotes remains unclear, owing to the lack of cultured representatives and corresponding physiological insights. Here we report the decade-long isolation of an Asgard Candidatus archaeon related to Lokiarchaeota from deep marine sediment. The archaeon -' Prometheoarchaeum syntrophicum' strain MK -D1 - is an anaerobic, extremely slow-growing, small coccus (around 550 nm in diameter) that degrades amino acids through syntrophy. Although eukaryote-like intracellular complexes have been proposed for Asgard archaea, the isolate has no visible organelle-like Ca structure. Instead, . P. syntrophicum is morphologically complex and has unique protrusions that are long